Fourdrinier paper making machines include a forming section which is defined by an endless foraminous belt, which is trained about a plurality of table rolls and usually suction boxes and other water removing devices to form a flat drainage surface onto which a slurry of paper making fibers and liquid is deposited, a series of tensioning and return rolls positioned beneath the forming surface, and breast and couch rolls positioned adjacent the upstream and downstream ends, respectively, of the forming surface.
The forming section of a paper making machine can vary substantially in size from under 100 inches to over 400 inches in width and over 100 feet in length. The replacement of the foraminous belt, commonly called a "fabric" or "wire", can be an expensive and time consuming operation.
One approach to this task has been to manufacture the machine such that all of the rollers, suction boxes and other liquid removing elements can be removed so that the fabric can be slipped over the ends of the rollers remaining and the elements which were removed reinserted within the loop of the fabric. Obviously such an approach is extremely expensive in terms of both the length of time a machine is out of operation and the amount of labor required to perform a fabric change.
Another more recent approach is to form the framing of the fourdrinier as a cantilever. A fourdrinier constructed in this manner is manufactured with supporting beams of sufficient strength so that, when properly anchored back of the machine, they can support the forming section as a cantilevered load during a fabric change. The front side framing is provided with supporting blocks which can be removed to allow a new fabric to be positioned on the machine.
Although the cantilever approach greatly facilitates the fabric change operation itself it will be apparent that because of the loads imposed on the machine and its foundation during fabric change the capital costs involved are substantial as compared to a non-cantilevered machine.